This invention relates to reflective devices that, when coupled with a transducer, are capable of redistributing and broadly dispersing sound over a broad spectrum of frequencies with little or no distortion.
It is well known in acoustics that the dispersion pattern of a sound source is related to the size of the radiating element. This causes conventional electro-acoustic transducers, or loudspeakers, to have an off-axis response that degrades with increasing frequency. This has long been regarded as a basic problem in loudspeaker design and over the years several different solutions have been proposed. These include the use of multiple transducers, horns and waveguides, electrostatic elements, and acoustic reflectors of varying shapes. Many of these solutions have undesirable side effects such as the introduction of frequency response anomalies and complicated fabrication techniques. Furthermore, these systems as well as conventional loudspeakers can act in unpredictable ways in typical listening environments due to the lack of consideration usually given to the human auditory perceptual system.
The recreation of sound via loudspeakers can be enhanced by controlling the direction, amplitude and spectral content of the sound arriving at the listener""s ears via the loudspeaker/listening environment combination. It is the purpose of this invention to address all these issues in a single device which is simple to manufacture. When properly mated to a suitable conventional transducer, the invention causes sound to be transferred to the listening environment with a nearly frequency-invariant horizontal dispersion pattern. This affords a greater number of listeners with timbrally accurate sound with a greater sense of envelopment due to greatly enhanced lateral room reflections. Furthermore, floor and ceiling reflections are reduced causing increased stereophonic phantom image stability.
A number of the invention""s features can be modified to suit the designer""s particular needs when incorporating the invention into a complete loudspeaker system. For example, modifications to the inventive system may be made to agressively control the vertical directivity of the loudspeaker system. Control of vertical directivity is particularly important in the areas of sound reinforcement and public address systems. Additionally, the inventive system may be used with transducers such as microphones to adapt the system for use as a sound receiving device.
The present invention addresses these concerns by providing an apparatus for the redistribution of acoustic power which comprises a base, a lens, and a means for mounting the lens upon the base. The base has an upper surface, a lower surface, a front surface, and a rear surface. The rear surface of the base is positionable upon a supporting surface. The lens also has an upper surface, a lower surface, a front surface, and a rear surface.
The front surface of the lens includes a reflective surface, a point P lying on the reflective surface, and at least one adjoining surface S1. A line L passes through the point P and intersects the lower surface of the base at a point B. A point F1 lies on the line L between the point P and the point B. The reflective surface is defined by the surface of revolution R1 of an elliptical arc A1 rotated about the line L through an angle xcex11 and the surface of revolution R2 of an elliptical arc A2 rotated about the line L through an angle xcex12. The elliptical arc A1 constitutes a portion of an ellipse E1 having a focal point located at the point F1 and having a lower end terminating at the point P. The elliptical arc A2 constitutes a portion of an ellipse E2 having a focal point located at said point F1 and having an upper end terminating at said point P. The angle xcex11 is chosen such that the surface of revolution R1 is convex with respect to adjoining surface S1, and the angle xcex12 is chosen such that the surface of revolution R2 is concave with respect to adjoining surface S1.
A primary object of the present invention is to provide an apparatus which redirects acoustic energy radiated from a sound radiator positioned at or proximate to focal point F1 such that the resulting dispersion pattern is very broad over a very wide frequency range horizontally and is limited vertically.
A further object of the present invention is to provide an apparatus which produces horizontally redirected acoustic radiation which is substantially free of frequency response anomalies.
Another object of the present invention is to provide an apparatus with insulative surfaces positioned to tailor the overall acoustic radiation pattern.
Yet another object of the present invention is to provide a loudspeaker system which demonstrates highly controlled vertical directivity.
A further object of the present invention is to provide a sound receiving device with a receiving pattern which is very broad over a very wide frequency range horizontally and is limited vertically.
Other objects and advantages of the present invention will become apparent when the apparatus for redistribution of acoustic radiation of the present invention is considered in conjunction with the accompanying drawings, specification, and claims.